<?php
$arr = array(
	array(
		"id"=>"1",
		"value"=>21
	),
	array(
		"id"=>"2",
		"value"=>22
	),
	array(
		"id"=>"4",
		"value"=>23
	)

);

//比如增加一个 sex 的值
foreach ($arr as $key => &$value){
	$value['sex'] = 'man';
}
//print_r($arr);

foreach ($arr as $key => $value) {
	$arr[$key]['sex'] = 'man';
}
//print_r($arr);